| Self-capacitance | Detects a change in capacitance between an electrode and ground when a finger approaches or touches the surface. | Touch buttons, control panels, appliances | Exposed electrodes, sensor traces, and the controller input can couple transient energy into the sensing circuit. | ±8 kV air discharge is a standardized test level; passing it depends on the complete product design and test setup. |
| Mutual-capacitance | Measures a change in coupling between transmitting and receiving electrodes. | Multi-touch panels, displays, touch interfaces | Electrode layout, panel grounding, controller protection, and cable routing influence the result. | Evaluate the assembled interface at the selected IEC test levels; the sensing method alone does not establish an ESD rating. |
| Resistive touch | Pressure brings conductive layers into contact, changing the measured resistance or voltage. | Industrial terminals, control panels, equipment used with gloves | The touch surface, flexible layers, connector, and measurement electronics may provide paths for transient coupling. | ±8 kV air can be included as a test point where appropriate; report results only for a tested product configuration. |
| Infrared optical | Detects interruption or reflection of infrared light near the touch surface. | Large displays, public kiosks, frames around displays | Emitter and receiver electronics, wiring, and exposed frame structures require attention. | ESD performance is determined by enclosure, grounding, protection, and the applicable test points—not by optical sensing alone. |
| Piezoelectric | Uses electrical charge generated by mechanical stress, such as a press or tap. | Sealed buttons, metal-panel controls, rugged interfaces | Piezoelectric elements and high-impedance signal inputs may need suitable circuit protection and layout. | Test the complete switch assembly and connected electronics; ±8 kV air is a standardized IEC test level. |
| Surface acoustic wave (SAW) | Detects touch by sensing changes to acoustic waves traveling across a surface. | Specialized touch screens and glass interfaces | Transducers, their connections, and the controller are potential coupling points for ESD transients. | Use product-level IEC testing to establish immunity; the sensing principle does not imply a particular pass level. |
| Ultrasonic touch | Uses ultrasonic signals and detects changes caused by contact with or interaction at a surface. | Specialized panels, interactive surfaces | Acoustic transducers, signal paths, and exposed conductive parts can affect ESD behavior. | Choose test points according to the product’s use and accessible surfaces; document the tested configuration. |
| Inductive touch | Detects changes in an electromagnetic field or inductance near a conductive sensing element. | Metal-surface controls, sealed interfaces | Coils, sensor circuitry, enclosure bonding, and nearby conductive structures influence transient coupling. | Assess the finished assembly using the applicable IEC 61000-4-2 method and selected test levels. |
| Force-sensing touch | Detects applied force using a force-sensitive resistor, strain element, or related pressure sensor. | Pressure-sensitive buttons, human-machine interfaces | Sensor leads and analog front-end inputs may be susceptible; mechanical force sensing does not itself specify ESD immunity. | ±8 kV air may be used as a test level when relevant; immunity must be verified by testing the product. |
| Optical image-based touch | Uses cameras or optical sensors to locate a touch or gesture from changes in an observed surface or field. | Interactive walls, large-format displays, gesture interfaces | Camera modules, interface cables, exposed frames, and system grounding are relevant design considerations. | Test accessible points on the assembled system; an IEC test level is not a guaranteed performance claim. |
| Comparison note: IEC 61000-4-2 defines ESD immunity test methods and levels. Its standard level set includes ±8 kV air discharge; this is a test level, not an automatic pass criterion for every touch-switch type. Actual robustness depends on the complete product, test points, setup, and acceptance criteria. Consult the applicable edition of the standard and product requirements. |